Means and method for making electri-
cal connections including weld pro-
jection means at the distal end sur-
face of the shank



Sept. 26, 1967 M. R. DUVAL 3,344,250

MEANS AND METHOD FOR MAKING ELECTRICAL CONNECTIONS INCLUDING I WELD PROJECTION MEANS AT THE DISTAL END SURFACE OF THE SHANK Original Filed June 27, 1963 "\Q' E. [2 94 6 4 58 1 50 0 I INVENTOR. Maw-A60: A, auwm WIT/V553. 42736 United States Patent C) MEANS AND METHOD FOR MAKING ELECTRI- CAL CONNECTEONS INCLUDING WELD PRO- JECTIUN MEANS AT THE DISTAL END SUR- FACE OF THE SHANK Montague R. Duval, St. Petershnrg, Fla, assignor to Texas Instruments Incorporated, Dallas, Tex., a corporation of Delaware Continuation of application Ser. No. 291,202, June 27, 1963. This application June 28, 1966, Ser. No. 561,291

Claims. (Cl 2tlll113) This application is a continuation of the commonly owned copending application Ser. No. 291,202, filed June 27, 1963, now abandoned, in the name of Montague R. Duval.

This invention relates to thermostatic devices and more particularly to improved means and methods of making electrical connections for such devices.

It is an object of the instant invention to provide a simple and inexpensive method and means for electrically connecting an electrically conductive member to a thermostatic element.

It is another object of the instant invention to provide a simple, economical and improved means and method for electrically connecting an electrically conductive member to a thermostatic element without upsetting or deleteriously afifecting the calibration of the thermostatic element.

Other objects will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the elements and combinations of elements, steps and sequences of steps, features of construction and manipulation, and arrang ments of parts, all of which will be exemplified in the structures and methods hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings in which one of the various possible embodiments of the invention is illustrated:

FIG. 1 is a bottom plan view of a welding rivet according to this invention;

FIG. 2 is a sectional View taken on line 22 of FIG. 1;

FIG. 3 is a top plan view of an assembly utilizing the welding rivet shown in FIGS. 1 and 2;

FIG. 4 is a view, partially in section, taken along line 4-4 of FIG. 3;

FIG. 5 is a top plan View of a switch employing the assembly shown in FIGS. 3 and 4 and with the cover of the switch removed for clarity of illustration; and

FIG. 6 is a sectional view taken on line 6-6 of FIG. 5.

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Dimensions of certain of the parts as shown in the accompanying drawing have been modified for the purposes of clarity of illustration.

Referring now to FIGS. 3 and 4 of the drawings, there is shown an exemplary assembly having an electrical connection according to this invention which assembly comprises an electrically conductive member such as, for example, an electrically conductive terminal ltl and a thermally responsive composite member such as, for example, a snap-acting thermostatic element generally indicated at 12. Composite or bimetallic element 12 includes a non-developable, deformed or dished portion which is responsible for its snap action and may, for example, be an inherently snap-acting thermostatic disc of the type described in US. Patent No. 1,448,240 to Spencer. As is well known in the art, such elements will snap at predetermined temperature conditions in response to changes in temperature. Such changes in temperature may, for ex- 3,344,250 Patented Sept. 26, 1967 ample, result from any one or a combination of heat generated by the flow of an overload current through the element, heat derived from an adjacent electrical heater and heat from the ambient environment. The temperature at which element 12 will snap is determined at least in part by the amount and nature of the deformation provided in the element. If element 12 is subjected to excessive heat concentrations and/ or excessive forces (e.g., mechanical pressures) such as might be encountered, for example, during welding, brazing or soldering operations or the like, the snap-acting characteristics of element 12 may be adversely affected.

It has been found that when an electrically conductive member such as terminal 16 is welded directly to a thermostatic or bimetallic snap-acting member such as element 12, there may result an undesirable stress change in the thermostatic disc which undesirably and deleteriously changes the calibrated conditions at which snapping will occur. This problem particularly manifests itself when the thermostatic bimetal of which element 12 is formed is of a comparatively thin gauge, e.g., on the order of .O06-.008. The problem is accentuated since such thin gauge material generally does not provide suflicient means or mass for direct welding purposes, The present invention advantageously overcomes, or at least minimizes, these problems.

Thermostatic element 12 is provided, adjacent one end thereof, with an aperture 14 which is adapted to receive therethrough the generally cylindrical shank portion 16 of an electrically conductive welding slug or rivet which is generally indicated by reference numeral 18 and is secured and electrically connected to element 12 at a plurality of spaced points 21, for example, as by welding. An electrical contact 19 is secured and electrically connected to element 12 adjacent its other end, for example, as by welding. The free projecting end of shank 16 is secured and electrically connected to electrically conductive support terminal 10, for example, as by welding to cantilever mount element 12 on support portion 10:: of terminal 10.

Referring now to FIGS. 1 and 2, there is shown an exemplary rivet or welding slug 18 formed of a suitable electrically conductive readily weldable material such as, for example, steel or a high nickel-copper corrosion resistant alloy such as that sold under the trademark Monel. Rivet 13 includes a head portion 20 on one side of which is provided the shank portion 16. The other side of head 20 may optionally include an indexing or locating means, for example, in the form of a recess 23 to facilitate automated assembly procedures. Another suitable form of an indexing or locating means is a welding projection (not shown) which may be of any desired shape such as, for example, a conical or hemispherical shape or a fiat, raised portion. The rivet 18, as illustrated in FIGS. 3-6, does not include any indexing or locating means. Head 20 is provided with a first weld projection mean in the form of a plurality of spaced weld projections 21a which may, for example, have a diamond, conical or other suitable shape. Rivet 18 also has second weld projection means provided on the free end of shank 16 and which may, take the form of a generally hemispherically shaped projection 22 or the like.

As can be seen in FIGS. 3 and 4, shank 16 is disposed within aperture 14 with weld projections 21a in contact with the surface 24 of element 12. In carrying out the invention it is important that aperture 14 be sufiiciently larger than the cross sectional dimensions of shank 16 so that the latter may be loosely confined within the former without contact therebetween before or during the welding operation. Thus contact between rivet 18 and thermostatic element 12 is limited to weld projections 21a. Shank 16 is also of suflicient length such that the free end thereof protrudes or projects beyond the surface 26 of thermostatic element 12 when the shank is disposed within the aperture 14 and projections 21a are in engagement with surface 24 of thermostatic element 12. The free end of shank 16 provides an annularly extending shoulder 17 which abuts and maintains terminal support portion 10a in a spaced relationship with respect to thermostatic element 12 as can be seen in FIGS. 4 and 6.

The following method of assembly illustrates the invention.

A blank from which thermostatic element 12 is formed is selected. Thereafter rivet 18 and contact 19 are respectively welded to element 12 as shown in FIGS. 3 and 4, for example, as by resistance welding. It will be noted that shank 16 is maintained out of engagement with element 12. The projections 21a (which are consumed during the welding process) serve as Weld points and fixedly secure the rivet to the thermostatic element to provide a secure electrically conductive connection therebetween. It is to be noted that this arrangement provides minimum heat conductive contact between the thermostatic disc and the rivet while providing a good electrical connection therebetween.

After rivet 18 has been secured to the thermostatic element 12, the latter is defromed to provide the non-developable or dished portion responsible for its snap action. At this point, the thermostatic element has been calibrated or set to operate (or snap) at a particular temperature which temperature setting, as noted above, is dependent at least in part upon the character or nature of the deformation.

After deformation and temperature setting of the thermostatic element 12, the electrically conductive terminal 10 is electrically connected to thermostatic disc 12 by welding shank 16 to terminal support portion 1% at weld projection 22 which is consumed during the welding step.

The heat and forces generated during the welding step are localized in the area of the weld projection 22. The weld projection 22 thus advantageously serves to isolate and protect element 12 from the intense heat, welding flash and forces generated during the welding operation which could deleteriously alter the calibration or snap-acting characteristics of element 12. Shoulder 17, by maintaining terminal portion 11111 in spaced relationship with respect to thermostatic element 12, and shank 16, in being maintained out of contact with the sides of aperture 14 in thermostatic element 12, additionally co-operate to provide the desired isolation and protection of element 12 described above. While there may be some flow of material about the oversized aperture 14 during the Welding operation, the dimensions of the aperture are sufficiently larger than the shank cross section to avoid engagement of this material with the element 12 which could undesirably stress element 12. In this manner, the electrical connection of terminal 10 to disc 12 is accomplished without deleteriously altering the calibration and temperature setting of thermostatic element 12.

It will be understood that the means and method described above has wide application and may be employed wherever it is desired to electrically connect an electrically conductive member to the thermostatic element. By way of example, the subassembly shown in FIGS. 3 and 4 may be incorporated into a switch generally indicated by reference numeral 39 and shown in FIGS. and 6. Switch 30 is the subject of and is more fully described in copending application Ser. No. 291,022, now Patent No. 3,288,967, entitled, Electrical Switch, filed in the name of Frederick G. Perry and assigned to the assignee of this application, to which reference may be had for further details of switch 30.

Briefly, switch 30 generally comprises a base 50 and a cover member 52, both formed of an electrically insulating material such as a phenolic moldable resinous material. Terminal is received within a suitable aperture provided in base to firmly mount terminal 10 and the thermostatic element assembly shown in FIGS. 3 and 4 on the base. Base 5d mounts second and third electrically conductive terminals 54 and 56. Each of terminals 10, 5 -1 and 56 includes portions extending exteriorly of base 50 to facilitate electrical connection of switch 30 in an electrical circuit.

Terminal 54 provides an electrically conductive contact portion 58 which is positioned for mating engagement with contact 19 carried by terminal element 12. As is more fully described in the above referred to copending application, switch 31 includes an adjusting screw 66 mounted on base 50 and positioned for engagement with support portion ltia for effecting further calibration of the snap-acting thermally responsive element 12.

Another advantage of this invention is that an electrical resistance heater wire 28 may be electrically connected to element 12 by welding one end of heater 28 to head 20 of rivet 18. As is more fully described in the above noted application, this advantageously also provides a direct heat conductive path between the heater element 28 and the thermal element 12. The other end of heater 28 is electrically connected to terminal 56, for example, as by welding to complete the electrical circuit. Again, the rivet construction with its minimum contact with thermostatic element 12 will isolate and protect element 12 from excessive heat and forces generated during welding of the heater to the rivet which could tend to deleteriously shift or affect the calibration of element 12.

It is to be understood that, if desired, other forms of welding projections than the diamond or conical shaped projections 21a may be provided. Such other forms, for example, might comprise an annular welding ring. Weld projection 22 may also take other forms such as, for example, a conical or diamond shaped from.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results are obtained.

As many changes could be made in the above constructions and methods without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense, and it is also intended that the appended claims shall cover all such equivalent variations as come Within the true spirit and scope of the invention.

It is to be understood that the invention is not limited in its application to the details of construction and arrangement of parts illustrated in the accompanying drawings, since the invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation.

I claim:

1. A thermostatic member comprising an electrically conductive welding slug having a head and and a shank of selected length extending from a side of said head, said slug having weld projections on said side of said head spaced from said shank, said slug shank having a distal end forming a surface and having weld projection means thereon spaced from the edges of said surface, a calibrated snap-acting bimetallic thermostatic element having an aperture therein located over said slug shank in spaced relation to said shank and having one side of said element Welded to said weld projections on said side of said slug head, said thermostatic element being thin relative to said shank length to be spaced from said shank end surface, and an electrically conductive terminal means abutting said shank end surface and having one side welded to said weld projection means on said surface for holding said terminal means in electrically conductive relation to said thermostatic element spaced from said thermostatic element to permit free snap-acting of said element.

2. A thermostatic member for attachment to an electrically conductive terminal means comprising an electrically conductive welding slug having a head and a shank of selected length extending from a side of said head, said slug having weld projections on said side of said head spaced from said shank, said slug shank having a distal end forming a surface adapted to engage said terminal means for locating said terminal means and having weld projection means on said surface spaced from the edges of said surface to be welded to one side of said terminal means, and a calibrated snap-acting bimetallic thermostatic element having an aperture therein located over said slug shank in spaced relation to said shank and having one side of said element welded to said Weld projections on said side of said slug head, said thermostatic element being thin relative to said shank length to be spaced from said shank end surface.

3. An electrically conductive welding slug for electrically connecting a calibrated snap-acting bimetallic thermostatic element of selected thickness having an aperture therein to an electrically conductive terminal means for permitting free snap-acting of said thermostatic element said slug comprising a head and a shank of selected length extending from a side of said head, said slug having weld projections on said side of said head spaced from said shank to be welded to one side of said thermostatic element, said shank being of selected cross-section to extend through said element aperture in spaced relation to said element, said slug shank having a distal end forming a surface adapted to engage said terminal means for locating said terminal means in spaced relation to said thermostatic element, said shank end surface having weld projection means thereon spaced from the edges of said surface to be welded to said thermostatic element.

4. A method for electrically connecting a snap-acting bimetallic thermostatic element to an electrically conductive terminal means for permitting free snap-acting of said element in response to selected temperature conditions, said method comprising the steps of fitting a welding slug having a head, a shank of selected length extending from a side of said head, and weld projections on said side of said head spaced from said shank through an aperture in said thermostatic element so that one side of said element engages said weld projections with said shank spaced from said element and so that a distal end surface of said shank having weld projection means centrally located thereon is spaced from said element, welding said one side of said element to said weld projections on said side of said head, calibrating said thermostatic element to snap-act in response to said selected temperature conditions, and welding said terminal means to said weld projection means on said shank end surface so that said terminal means abuts said surface for holding said terminal means in spaced relation to said thermostatic element.

5. A method as set forth in claim 4 wherein said thermostatic element is selectively deformed for calibrating the element to snap-act in response to said selected temperature conditions.

References Cited UNITED STATES PATENTS 1,968,976 8/ 1934 Van Halteren 219-93 2,564,931 8/ 1954 Smith 200-438 2,740,034 3/ 6 Carlyle 21993 2,800,555 7/1957 Sundt 200122 3,107,282 10/ 1963 Desio 200-413 3,288,967 11/ 1966 Perry 200-413 3,299,239 1/ 1967 Mawney et a1 200-113 OTHER REFERENCES German application: 1,138,707, 10/1962, Muller-Borner.

Reich-Modern Projection Welding, Welding Journal, August 1948.

BERNARD A. GILHEANY, Primary Examiner.

H. A. LEWITTER, Assistant Examiner. 

1. A THERMOSTATIC MEMBER COMPRISING AN ELECTRICALLY CONDUCTIVE WELDING SLUG HAVING A HEAD AND AND A SHANK OF SELECTED LENGTH EXTENDING FROM A SIDE OF SAID HEAD, SAID SLUG HAVING WELD PROJECTION ON SAID SIDE OF SAID HEAD SPACED FROM SAID SHANK, SAID SLUG SHANK HAVING A DISTAL END FORMING A SURFACE AND HAVING WELD PROJECTION MEANS THEREON SPACED FROM THE EDGES OF SAID SURFACE, A CALIBRATED SNAP-ACTING BIMETALLIC THERMOSTATIC ELEMENT HAVING AN APERTURE THEREIN LOCATED OVER SAID SLUG SHANK IN SPACED RELATION TO SAID SHANK AND HAVING ONE SIDE OF SAID ELEMENT WELDED TO SAID WELD PROJECTIONS ON SAID SIDE OF SAID SLUG HEAD, SAID THERMOSTATIC ELEMENT BEING THIN RELATIVE TO SAID SHANK LENGTH TO BE SPACED FROM SAID SHANK END SURFACE, AND AN ELECTRICALLY CONDUCTIVE TERMINAL MEANS ABUTTING SAID SHANK END SURFACE AND HAVING ONE SIDE WELDED TO SAID WELD PROJECTION MEANS ON SAID SURFACE FOR HOLDING SAID TERMINAL MEANS IN ELECTRICALLY CONDICTIVE RELATION TO SAID THERMOSTATIC ELEMENT SPACED FROM SAID THERMOSTATIC ELEMENT TO PERMIT FREE SNAP-ACTING OF SAID ELEMENT. 